Postemergence Weed Control In Alfalfa

By Bruce Anderson

Extension Forage Specialist

Are you finding weeds in your new alfalfa?  Vigorous weed growth this spring may make it extra tough for your seedlings as weeds reduce growth of new alfalfa by shading and competing for moisture.

When weeds, especially broadleaf weeds, threaten seedling alfalfa, mowing is often used for control. Adjust mowing height so several leaves remain on alfalfa seedlings after clipping to help your alfalfa seedlings regrow rapidly. Also, do not smother small seedlings with clippings. Mow weeds before they get so tall that they produce a large quantity of clippings.

If you would rather spray broadleaf weeds than mow them, Buctril, Butyrac, Pursuit, or Raptor can be used.  Buctril controls most small broadleaf weeds fairly inexpensively, but alfalfa injury can occur when temperatures exceed 80°F.  If you expect those high temperatures when you spray, it might be better to use Butyrac, Pursuit, or Raptor.  These herbicides control most small broadleaf weeds, although results will be inconsistent with over three inches tall. Pursuit and Raptor are more expensive, but their residual soil activity will continue to control weeds throughout much of the season.

Mowing is not very effective with grassy weeds, so use Poast Plus or Select to kill grassy weeds.  Make sure you spray before grasses are 4 inches tall or control will be spotty.

You can prevent these problems by acting quickly.  Examine your fields soon and control weeds as needed.

Source:unl.edu